The functional circuits considered here are, for example, amplifiers, voltage or current sources, etc., for which it is possible to adjust, for example, an input resistance or an output reference potential through the programming of programmable elements provided for this purpose. These elements are, for example, one-time programmable fuses or antifuses. The adjusting of the parameter or parameters is done after packaging of the functional circuit in a plastic pack, through the application of appropriate control signals to the standard pins of the packaged circuits. The programming of one or more programmable elements thus makes it possible to compensate for any drift in the parameter considered that may have appeared during the packaging of the circuit and thus enables high precision to be obtained for the parameter, i.e. precision at least as high as that obtained after adjustment during the silicon wafer sorting process. One exemplary embodiment of an adjustment device intended for this purpose is described in the patent application FR2795557.
A programming circuit is therefore used to adjust a parameter of the functional circuit by programming a fuse (or antifuse) of the functional circuit. This programming typically includes the application of a high voltage to the terminals of the fuse, at a level sufficient to disrupt or blow the fuse, i.e. to make it change its state.
The drawback of using such a programming circuit is that, due to the high potential used, the integrated circuit no longer meets the relatively stringent standards laid down for the protection of individuals, especially their protection from electrostatic discharge. These standards impose a borderline value on the potentials that appear in an integrated circuit, this value being lower than the potential needed to program adjustment fuses.
What is desired is an adjustable circuit that can resolve this problem.